Tuning the Electrical Properties of Cellulose Nanocrystals through Laser-Induced Graphitization for UV Photodetectors

Laser-induced graphene from abundant and renewable biobased carbon sources may open the way for sustainable and low-cost electronic device generation. Yet little progress has been made on nanocellulose-based materials to produce laser-induced graphene (LIG). In this work, we demonstrate the versatility of the laser-assisted technique to promote graphitization of pineapple cellulose nanocrystals (CNCs), aimed at UV photodetectors. CNCs tablets are used as carbon-based precursors to photonically synthesize LIG nanopowders, which are used as functional materials in the formulation of printable cellulose composite electroconductive inks, using sodium carboxymethyl cellulose (CMC) as a binder. The developed CMC/LIG inks are used to pattern LIG electrodes (LIGE) on tracing paper, using hand-drawing techniques. The impact of the laser parameters in the conversion of the CNCs tablets into graphene nanopowder, as well as the influence of the CMC/LIG ink composition allied with an additional laser treatment on the chemical, morphological, and electrical properties of the hand-drawn cellulose composite films is systematically addressed. The LIG nanopowder composite films reveal less sheet resistance after laser treatment. The optimal conditions were found for 0.6 w/v% of LIG nanopowder in CMC solution at +1.1 mm defocus, 8.2 cm/s tip laser speed and 2.4 W CO2 laser power. As a proof-of-concept, fully printed zinc oxide UV photodetectors with the optimized LIGE are demonstrated, showing a superior performance in comparison to other UV sensors described in the literature.